Definition
A dimensionless number that represents how effectively a wing produces lift at a given angle of attack and configuration. It captures the combined effect of airfoil shape, angle of attack, and high-lift devices (such as flaps), and appears as one of the variables in the lift equation: L = CL × ½ρV²S.
Plain English
A number that tells you how much lift the wing is producing for its current shape and angle to the oncoming air. A higher number means the wing is working harder for each unit of speed and air density; a lower number means it is producing less lift for the same conditions.
Context Anchor
Seen in the lift equation when explaining how lift depends on air density, airspeed, wing area, and the wing’s ability to produce lift.
Derivation
‘Coefficient’ comes from Latin roots meaning ‘working together with’ — a multiplier that combines with other values to give a result. Here it is the multiplier in the lift equation that captures everything about the wing’s shape and angle, separate from speed, air density, and wing area.
Why Pilots Care
Understanding how the coefficient changes with angle of attack lets pilots control lift without altering airspeed or wing area.
Analogy
Think of CL like a wing’s grip on the air. Speed and wing size matter, but CL describes how effectively the wing is using the air it has.
Grounding Statement
If the airplane slows down, the wing may need a higher CL to keep supporting the airplane.
Intuition Check
CL is not the total amount of lift. It is the lift-effectiveness factor used inside the lift equation.
Example Sentence 1
As the pilot increased the angle of attack on final approach, the coefficient of lift rose, allowing the aircraft to maintain lift at a slower airspeed.
Example Sentence 2
During cruise the wing operates at a modest coefficient of lift because high speed supplies most of the required force.